Black Fire Storm

A Black Dragon made up of sheets of roaring flame appears in a location you choose within range. 

Each creature in the area must make a Dexterity saving throw. It takes [roll]5d20[/roll] fire damage on a failed save, or half as much damage on a successful one.

The fire damages objects in the area and ignites flammable objects that aren't being worn or carried. If you choose, plant life in the area is unaffected by this spell.

Each target hit by the spell also takes [roll]3d6[/roll] of fire damage at the end of the round and the round after being hit.